Radial seal air filters are often used to filter air in air intake systems of devices, such as internal combustion engines. Conventional radial seal air filter systems include a filter cartridge having filter media arranged in a cylindrical manner and positioned between two end caps. The end caps often include polyurethane (“PU”) seals that separate the clean side of the air filter from the dirty side of the air filter when the filter cartridge is received in an air filter system housing. The housing is generally a plastic or metal container that includes an air inlet (i.e., to provide air to be filtered to the filter media) and an air outlet (i.e., to supply filtered air to the device or component). Some conventional radial seal air filter cartridges are fitted over (i.e., inserted over when provided in the system housing) or include (i.e., have built-in) secondary filters within the space formed in the cylindrical air filter media. The secondary filter elements may be cantilevered within the housing.
Although PU is relatively inexpensive, a significant volume is required to close off the end cap on larger air filter elements. Because the PU is rubber-like for good sealability, the center area of top end cap is very “spongy” and can be easily depressed. Although this is acceptable from a functional perspective, it can be perceived as a “lower quality” feature by certain end users. Further, in some arrangements, the conventional air filters are received in a housing having a cover such that the entire filter cartridge is encased by the housing and the cover. In these arrangements, it may be difficult for a manufacturer or technician to verify that a filter cartridge is properly fitted within the housing (e.g., prior to shipping an assembled unit). Still further, filter cartridges fitted over secondary filter elements (e.g., a cantilevered secondary filter element) are easily positionable incorrectly with respect to the secondary filter element, which affects filter service operations. In some arrangements, the secondary filter is pushed off center by uncontrolled PU expansion during the installation process.
The following listed U.S. Patents provide background relating to similar filters that may suffer from the above described disadvantages. Each of the following listed U.S. Patents are incorporated herein by reference in entirety.
U.S. Pat. No. 6,149,700 discloses a filter element that includes pleated filter media having a plurality of pleats in a closed annular loop having an outer perimeter defined by a plurality of outer pleat tips, and an inner perimeter defined by a plurality of inner pleat tips, the closed annular loop having a hollow interior extending along an axis, wherein fluid to be filtered flows laterally through the filter media and flows axially in the hollow interior. The filter element has an axial flow passage along the axis and circumscribing the hollow interior and has a flow perimeter greater than the inner perimeter of the filter element defined by the inner pleat tips. An end cap of resilient compressible material at the axial end of the filter element bears radially between and is radially compressed between an outer liner and a flow tube at the enlarged flow passage.
U.S. Pat. No. 6,383,244 discloses a filter that has a housing extending along an axis between first and second axial ends, and has a closed loop primary filter element extending axially in the housing, and a closed loop safety filter element in the hollow interior of the primary filter element. A detent member engages and retains the end cap of the safety filter element independently of the primary filter element to retain the safety filter element in housing upon removal of the primary filter element from the housing.
U.S. Pat. No. 6,391,076 discloses a full flow fluid filter that has a housing extending axially along an axis, and a pleated filter element having a plurality of pleats in a closed loop annulus having an outer perimeter defined by a plurality of outer pleat tips, an inner perimeter defined by a plurality of inner pleat tips, and a hollow interior extending along the axis. Fluid flows substantially directly axially through the filter element, with minimal bending and change of direction, minimizing flow restriction.
U.S. Pat. No. 6,416,561 discloses an open flow fluid filter that has a pleated main filter element having a plurality of pleats in a closed loop having an outer perimeter defined by a plurality of outer pleat tips, and an inner perimeter defined by a plurality of inner pleat tips. The loop has a hollow interior extending along an axis. Fluid to be filtered flows through the main filter element from an upstream dirty side to a downstream clean side, and flows axially in the hollow interior. The main filter element has an axial flow passage extending along the axis and circumscribing the hollow interior and has a flow perimeter greater than the inner perimeter. A safety filter element downstream of the main filter element filters both the axial flow in the hollow interior and additional flow between the flow perimeter and the inner perimeter. A filter with additional flow is also provided.
U.S. Pat. No. 8,241,377 discloses a filter element that has a reinforcement band or ring along at least a portion of the perimeter thereof and performing a support function thereat preventing or minimizing damage upon attempted percussive cleaning of the filter element by service personnel striking the perimeter against an impact surface. Alternatively, a failure band or ring is provided along at least a portion of the perimeter and performs a designated failure function to a failure condition thereat upon attempted percussive cleaning, with the failure condition providing at least one of: a) an indication to service personnel that the filter element has been damaged and should not be re-installed; and b) a deformed condition preventing re-installation.